Numerous embodiments of gas cooking assemblies equipped with gas-fired burners and a glass ceramic cook plate have been described, for example, in U.S. Pat. Nos. 3,468,298; 4,020,821; 4,083,355 and 4,201,184.
In gas-fired burners, the gas is combusted at the surface of a burner plate made of a porous ceramic. In a gas cooking assembly, one or more such gas-fired burners are mounted at a distance below a common glass ceramic plate known per se. A cooking position is defined by each burner at the upper side of the glass ceramic plate. Each individual gas-fired burner is secured by an ignition device and by a safety pilot against an unused away-flowing combustible gas mixture. The description of one such burner plate is presented, for example, in European patent publication 0,187,508.
The temperature of the radiating burner plate lies between approximately 900.degree. C. and 950.degree. C. depending upon the temperature resistance of the material. The maximum quantity of gas which call be metered to the burner is so limited by structural measures that a maximum operating temperature cannot be exceeded, for example, in order to protect the material of the burner plate or of the cooking plate and also to avoid unnecessary energy losses.
The permissible maximum temperature of glass ceramic cookplates lies usually between approximately 700.degree. C. and 750.degree. C. Temperatures of 900.degree. C. and more can occur within a short time span in the glass ceramic plate for pots having unsuitable and especially uneven bottoms and for unoccupied cooking positions with power set at high. For this reason, a temperature limiter is provided to protect the glass ceramic plate, which limiter reliably prevents overtemperatures of this kind.
Such temperature limiters are described in detail, for example, in U.S. Pat. No. 4,201,184.
In addition to a temperature limiter, a control of the power of the burner must be provided for the practical utilization for heating a cooking area.
Two principles are known with respect to controlling the power. According to one principle, the burner is operated continuously and the metered quantity of gas is reduced or increased in response to the required power. According to the other principle, the burner is driven in a clocked manner, that is, the burner is always driven with the maximum quantity of gas and the required power results from the ratio of switch-on time to switch-off time (pulse-duty factor).
German patent publication 3,315,745 discloses a cooking field having gas-heated burners and a continuous cooking plate made of glass ceramic or a comparable material. The cooking field has at least two clearly separated cooking zones to which corresponding separate burner locations are assigned. The cooking area further has a warm-holding zone and exhaust-gas channels for conducting the combustion gases away as well as auxiliary devices. The burner locations include combustion chambers, gas-mixing chambers, gas-mixing units and control units. The burner locations, the warm-holding zone and the exhaust-gas channels are enclosed at the locations thereof, which do not serve to conduct heat to the cooking field and at all locations of the burners, by a component common to these parts and made of a low-mass and heat-insulating material.
German patent publication 3,315,745 also discloses that a jet plate can be alternately produced from silicate fiber material. In this connection, reference may be made to column 6, lines 21 and 22, of this publication.
German patent publication 3,844,081 discloses a cooking apparatus having at least one cooking field comprising a burner pot seated in a burner plate, a nozzle plate and a ceramic plate mounted above the nozzle plate and spaced relative thereto. An intermediate base is arranged below the burner pot and a space is formed below the intermediate base for control and/or monitoring apparatus. An exhaust channel is provided for conducting the exhaust gases away. An essentially vertical shaft is provided at the rearward end of the cooking apparatus and this shaft can be connected to an exhaust channel or be configured as such. A fan is provided in the space for the control and/or monitoring apparatus. The fan draws cooling air in primarily through this space from the front end and presses this cooling air into the shaft. The shaft is configured as a flow channel in such a manner that the primary cooling air draws secondary cooling air in via the space between the burner plate and the intermediate base and conducts away the exhaust gas emanating from the space between the burner plate and the ceramic plate.
German patent publication 3,844,081 has the task to improve a cooking apparatus of the kind described with respect to the control of waste heat and to thereby improve the apparatus with respect to overall thermal design. A fan is utilized in order to remove only the exhaust gas with a relatively considerable complexity in structure.
U.S. Pat. No. 4,020,821 discloses positioning a blower in a gas cooking apparatus having a continuous plate, for example, made of glass ceramic. The blower brings in additional air for obtaining a good combustion of the gas. However, no gas-fired burners having burner plates are utilized; instead, burners with an open flame are utilized.
British patent publication 2,230,595 discloses a gas range having a glass ceramic plate and at least one gas-fired burner mounted closely beneath the plate. Each burner has a burner chamber with a high number of individual chambers. A burner plate of ceramic is mounted over the burner chamber and is perforated in correspondence to the arrangement of the chambers. Furthermore, the gas range has a gas supply and a fan device to always make combustion air available when the burner operates.
U.S. Pat. No. 4,020,821 as well as British patent publication 2,230,595 disclose the use of fans or blowers in gas cooking apparatus having continuous glass ceramic cooking plates. However, the overall arrangement of the cooking devices is very complicated and complex and therefore unreliable in practical use and expensive to produce.